Loss Differentiated Rate Adaptation in Wireless Networks

Data rate adaptation aims to select the optimal data rates for current channel conditions leading to substantial performance improvement. This paper proposes a data rate adaptation technique that: (1) exploits the periodic IEEE 802.11 beacons; (2) discriminates between frame losses due to channel fading and those due to collisions and takes actions appropriate for each type of loss; and (3) recommends and justifies the use of the lowest data rate for the very first retransmission after a frame loss. The last feature - namely retransmitting at the lowest data rate - helps in diagnosing the real cause of a frame loss. Moreover, this work analytically shows that retransmitting at the lowest data rate is more efficient, especially in poor SNR environments or when there is no knowledge of the cause of a loss (channel degradation or transmission collision). This scheme, dubbed loss differentiated rate adaptation (LDRA), is extensively evaluated through simulations and shown to perform better especially when network traffic is heavy.